1. Field of the Invention
The present invention relates to an image display device and displaying method, and more particularly to an image display device and displaying method of decoding binary image data compressed in the MPEG (Motion Picture Expert Group)-2, for displaying the same data.
2. Description of the Related Art
Roughly speaking, scanning method of a moving picture comprises a sequential scanning method and an interlaced scanning method (interlaced scan: skip scan). In the sequential scanning, all the pixels within one frame are the data of the same time; while, in the interlaced scan, image data of different time is repeated by turns in every other line. The image compression of the MPEG-2 supports the both methods; the CRT display of a computer, however, displays images in the sequential scanning, thereby deteriorating the image quality in displaying the interlaced scanned moving picture due to the motion between fields. Therefore, in order to prevent from this image degradation, it is preferable to perform scan conversion (this meaning will be described later) on a moving picture of the interlaced scan.
While, in a static image of the interlaced scan, there is no motion at any odd line and even line; therefore, it can be converted on a sequential scanning typed display, as it is, with no problem. It is preferable to display a static image as it is, without any scan conversion.
In this background, a method of detecting motion between frames of a moving image is disclosed in Japanese Patent Publication Laid-Open (Kokai) No. Heisei 06-205375, and Japanese Patent Publication (Kokai) Laid-Open No. Showa 62-72287 (hereinafter, referred to as article 1 and article 2 respectively). The method disclosed in the article 1 and the article 2 is a method for detecting motion of an image while comparing the pixel data of the current frame with that one of the prior frame, with the pixel data of the prior frame stored in advance. Further, an example of a digital moving image decoder is disclosed in Japanese Patent Publication Laid-Open (Kokai) No. Heisei 10-191257 (hereinafter, referred to as article 3).
The method disclosed in the article 1 and the article 2 is defective in using extra memory area because of requiring the processing for storing the prior frame into a memory. Further, it is defective in delaying the processing speed because of requiring the processing for detecting motion of the pixel data. The article 3 never includes a way for solving these defects.